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For more than a decade, the United States has relied mainly on voluntary action by private companies to protect the nation's critical cyber infrastructure, but "it's not working," a cybersecurity expert told lawmakers.

Companies own 85 percent of the critical infrastructure, and they have been unwilling to invest what is needed to protect against cyberattacks, James Lewis, a senior fellow at the Center for Strategic & International Studies, told the Homeland Security cybersecurity subcommittee on Wednesday.

That leaves key parts of the infrastructure, such as the electrical grid and financial institutions, vulnerable to crippling attacks, he said. Lewis heads the technology and public policy program at the Center for Strategic and International Studies.

"No sector has a greater incentive than banks to protect their networks," he said. "They are a constant target. Some banks, particularly top-tier banks, have sophisticated defenses. Despite this, they are hacked.

"If banks cannot protect themselves, why do we think other sectors will be able to do so?" Lewis asked.

Many companies don't try as hard as banks because investing in cybersecurity just doesn't pay off. It "requires them to spend on nonproductive assets. They will not get an increased return on investment" by installing cyber defenses, Lewis said, so they don't do it.

"Regulation is unpleasant, but in some cases, the alternative is worse. Cybersecurity is one such case," he said. The private sector should be given a substantial role in developing regulations for cybersecurity, but stronger rules are needed, Lewis said.

Lawmakers might use the approach developed for the Chemical Facilities Anti-Terrorism Standards, Lewis said. Those regulations set security standards for plants that produce high-risk chemicals, but also allow plant operators to propose alternative security plans.

The United States faces a number cyber risks. The most serious -- cyberwar -- seems unlikely. China and Russia both could launch damaging cyberattacks, for which the United States is not prepared, Lewis said. But they are unlikely to do so unless we were to get into a conventional war with them.

Terrorists so far lack the capability to launch cyberattacks. "If they had this capability, they would have already used it," he said.

The emergence of "virtualized IT infrastructure," or cloud computing, promises to put cyber defense into the hands of real experts, said Kwon, a former director of the United States Computer Emergency Readiness Team -- US-CERT -- in the Homeland Security Department, who now runs her own consulting business.

"Soon most companies, even government departments and agencies, will no longer have data centers, or continue to manage their own e-mail servers, applications or desktops," she said. Instead, they will buy those services from cloud providers.

If the move to the cloud is done correctly, security can be built into the services that companies and agencies buy, she said.

Cloud computing promises to cut the cost of security because costs won't be borne individually, but will be spread over multiple cloud customers, Kwon said. In the same way, cloud computing might ease the "cyber talent pool shortage." Companies won't need their own cybersecurity experts, the expertise will come with the cloud services.

"No longer will companies or departments and agencies with missions different from information technology need to be in the IT business," she said. Vendors will supply the appropriate infrastructure and services.

Rep. Daniel Lungren, R-Calif., cybersecurity subcommittee chairman, said the hearing marked the beginning of a subcommittee examination of possible solutions for defending U.S. cyberspace.

Rep. Yvette Clarke, D-N.Y., the senior subcommittee Democrat, said Congress and various presidents have been warned about cyber vulnerabilities in the past, but "what has been lacking is the courage and leadership to actually implement these recommendations."